Axle driving apparatus

ABSTRACT

An axle driving apparatus wherein a hydraulic motor and a hydraulic pump for a hydro-static-transmission are housed in a transmission casing of the axle driving apparatus and a center section for connecting the hydraulic motor and hydraulic pump is disposed in the transmission casing, the center section being fixed at the butt joint portion at the transmission casing, and an oil passage from the hydraulic pump to the hydraulic motor at the center section is bent at a right angle so as to extend the motor shaft in parallel to the axles, so that the rotation direction of the motor shaft conventionally changed by bevel gears is changed by the oil passages in the center section.

This application is a continuation, of application Ser. No. 08/775,859,filed Jan. 2, 1997, U.S. Pat. No. 5,752,417; which is a continuation ofapplication Ser. No. 08/449,013, filed May 24, 1995, U.S. Pat. No.5,694,816; which is a continuation of application Ser. No. 08/193,577,filed Feb. 7, 1994 (Now U.S. Pat. No. 5,473,964); which is acontinuation of Ser. No. 08/100,352, filed Jun. 21, 1993 (NowAbandoned); which is a continuation of Ser. No. 07/518,720, filed May 4,1990 (Now Abandoned); which is a continuation of Ser. No. 07/304,581,filed Feb. 1, 1989 (Now U.S. Pat. No. 4,932,209).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an axle driving apparatus with ahydro-static-transmission used as a driving apparatus for a vehicle suchas a light tractor.

2. Related Art

Conventionally, an axle driving apparatus, which vertically divides acasing thereof and journals axles at the divided surfaces and drives theaxles by a hydro-static-transmission attached to the casing, is wellknown as disclosed in, for example, the Japanese Utility ModelPublication Gazette No. Sho 62-44198 and the Japanese Patent Laid-OpenGazette Sho 62-101945, filed by the same applicant.

In the conventional apparatus, however, the hydro-static-transmission,separate from the axle driving apparatus, is fixed to the outsidethereof in a manner of being exposed, whereby the apparatus islarge-sized as a whole and larger in the gross weight. Also, it isrequired for driving the horizontally disposed axles by a motor shaft ofa hydraulic motor vertically disposed at the exterior, to interposebevel gears in a drive system for both the motor shaft and axles.

SUMMARY OF THE INVENTION

An object of the invention is to provide an axle driving apparatus whichcontains the hydraulic motor and a hydraulic pump of thehydro-static-transmission in a transmission casing of the axle drivingapparatus, and a center section for connecting the hydraulic motor andhydraulic pump is disposed in the transmission casing, the centersection being fixed to the butt joint surface of upper and lowersections of the casing.

The center section is formed in a L-like shape when viewed in sectionand an oil passage from the hydraulic pump to the hydraulic motor isbent at a right angle to thereby extend the motor shaft in parallel tothe driven axle. Hence, instead of conventional bevel gears used to turnthe rotation direction, the oil passage in the center section is used toturn the power transmitting direction.

In a case where the center section is fixed to the butt joint surfacesof the half casings, when the half casings are fixedly joined directlywith a center section of aluminum die casting by use of four bolts, thecenter section may be distorted, thereby using three tightening bolts.

The above and further objects and novel features of the invention willmore fully appear from the following detailed description when the sameis read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a light tractor attached with an axle drivingapparatus of the invention.

FIG. 2 is a sectional front view of the axle driving apparatus.

FIG. 3 is a sectional view taken on the line 3--3 in FIG. 2, in which anupper half casing is removed.

FIG. 4 is a sectional view taken on the line 4--4 in FIG. 3.

FIG. 5 is a sectional view taken on the line 5--5 in FIG. 3.

FIG. 6 is a sectional view taken on the line 6--6 in FIG. 3.

FIG. 7 is a sectional front view of a modified embodiment of the axledriving apparatus of the invention, in which the arrangement of thecheck valves is changed.

FIG. 8 is a plan view of the same.

FIG. 9 is a sectional view taken on the line 9--9 in FIG. 7.

FIG. 10 is a sectional view taken on the line 10--10 in FIG. 7.

FIG. 11 is a perspective exploded view of the axle driving apparatus ofthe invention.

FIG. 12 is a sectional front view of another modified embodiment of theinvention, in which a center section is fixed to the inner surface ofthe bottom wall of a lower half casing.

FIG. 13 is a plan view of the FIG. 12 embodiment.

FIG. 14 is a sectional front view of a further modified embodiment ofthe invention, in which a center section has three bolt-bores into whichthree fixing bolts are inserted so that the center section is fixedtherethrough to the upper half casing.

FIG. 15 is a plan view of the FIG. 14 embodiment.

FIG. 16 is a sectional plan view of the center section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, a light tractor loading thereon an engine E havinga vertical crank shaft is shown.

A pulley is fixed to the vertical crank shaft of the engine so that adriving power is transmitted from the pulley through a belt to a pulleyfixed to an input shaft, pump shaft 4 of a hydraulic pump P, projectingupwardly from an axle driving apparatus of the invention.

The tractor is provided at the front or under the body with a mower R orR' to thereby mow a lawn.

The present invention relates to an axle driving apparatus or transaxleand is specifically described herein as driving axles 13 of the tractor.

Next, the axle driving apparatus will be detailed of its construction inaccordance with FIGS. 1-6.

A transmission casing of the axle driving apparatus is formed in upperand lower half casings 1 and 2 (first and second casing sections), boththe casings being joined along a junction surface 2z (see FIGS. 3 and11) to form one closed-type transmission casing. As shown in FIGS. 1 and2, the junction surface is horizontally disposed when the casing isfixed to a vehicle.

Between the butt joint junction surfaces of the upper and lower halfcasings 1 and 2 are held bearings in parallel thereto, for the axles 13and a counter shaft 24; and a bearing 34 for one end of a motor shaft 5.As shown in FIGS. 2-5, the longitudinal axes (5x, 13x, and 24x,respectively) of the motor output shaft 5, axles 13, and countershaft 24are parallel to the junction surface, and are disposed within a singleplane, more particularly, the plane defined by the junction surface.

At the lower surface of the upper half casing 1 is formed a mountingsurface so that a center section 3 fixedly supporting the hydraulic pumpP and a hydraulic motor M is mountable to the mounting surface throughbolts 39 inserted into bolt holes 3g from below.

In the state where the center section 3, fixing thereto the hydraulicmotor M and hydraulic pump P, is mounted to the lower surface of theupper half casing 1, the lower half casing 2 is joined from below withthe lower surface of the upper half casing 1 in a manner of closing thelower half casing 2 and bolts are used to connect both the upper andlower half casings 1 and 2.

The upper and lower half casings 1 and 2 are formed by aluminum diecasting, whereby parts subjected to mechanical processing are reduced tolower the manufacturing cost.

The HST or hydrostatic type transmission stored within the axle drivingapparatus comprises the hydraulic pump P, center section 3 and hydraulicmotor M. The center section 3 is formed, so that a pump mounting surface3d formed on the center section 3 is parallel to the axles 13 and amotor mounting surface 3e formed on the center section 3 isperpendicular to the axles 13.

Pairs of crescent-shaped oil passages 3a' and 3b' and 3a" and 3b" areformed at the pump mounting surface 3d and motor mounting surface 3e,the pair of crescent-shaped oil passages 3a" and 3b" at the motormounting surface 3e and pair of crescent-shaped oil passages 3a' and 3b'at the pump mounting surface 3d being connected to two oil passages 3aand 3b to constitute a closed circuit fluid path.

A cylinder block 10 for the hydraulic pump P is rotatably mounted on thepump mounting surface 3d and pistons 12 are inserted vertically slidablyinto a plurality of piston holes at the cylinder block 10 respectively.

When the pump shaft 4, supported by a bearing 31 at the upper halfcasing 1 and a spherical bush 32 at the pump mounting surface 3d, isrotated, the cylinder block 10 and pistons 12 rotate.

A thrust bearing 15 abutting against the upper end of each piston ischanged at an angle by a swash plate 9, so that the discharge rate anddischarge direction of the hydraulic pump P are changed to supply thedischarged pressure oil from the oil passages 3a' and 3b' at the centersection 3 to the hydraulic motor M through the oil passages 3a and 3b.

As shown in FIG. 4, the swash plate 9 is changeable of its angle througha positioning plate 6a in association with rotation of a speed changelever shaft 6, a detent unit 20 for holding the neutral position of thespeed change lever shaft 6 being constituted in the upper half casing 1.

The detent unit 20 is fitted into a recess 6b at the positioning plate6a, thereby enabling the neutral position to be ensured.

As shown in FIGS. 2 and 3, a short-circuit valve 25 of slidable selectorvalve for short-circuiting between the two oil passages 3a and 3b at thedischarge side and the return side is disposed, so that when the valve25 is open, generation of the state where the hydraulic motor M side isdriven to send the pressure oil toward the hydraulic pump side can beavoided.

Reference numeral 7 designates a control for operating the short-circuitvalve 25.

The short-circuit valve 25 and control 7 are slidably operated to push,to be engageable, or pull, without engagement, in order to becontrollable in the abutting condition. Such construction enables simpleassembly of the apparatus.

Between the oil passages 3a and 3b at the center section 3 areinterposed check valves 26 and 27 to form an oil feed route 30, andbetween the check valves 26 and 27 is bored an operating oil suctionport 3c extending downwardly.

In the lower end of operating oil suction port 3c is fitted an oilfilter 8 formed of a spongy fine-porous material, the oil filter 8contacting with the lower half casing 2 so as to be held thereto.

Thus, the oil filter 8, operating oil suction port 3c and check valves26 and 27 are provided to communicate with the oil passages 3a and 3bthrough the check valves 27 and 27, whereby in a case where thehydraulic motor M and hydraulic pump P operate and the operating oilleaks from the interior of the closed circuit so as to decrease, the oilpassage 3a or 3b generates therein negative pressure so that lubricatingoil in the casing is taken in as the operating oil.

In addition, reference numeral 0 designates an oil level of lubricatingoil filled into the transmission casing (FIG. 2).

The pump mounting surface 3d at the center section 3 is somewhat largerin its flat surface to also serve as the surface through which thecenter section 3 is mounted to the lower surface of the upper halfcasing 1.

A cylinder block 11 is rotatably mounted onto the motor mounting surface3e at the center section 3, and pistons 14 are slidably fitted into aplurality of piston holes at the cylinder block 11 and always abut atthe heads against a thrust bearing 16. In such construction, the pistons14 push the thrust bearing 16 through the pressure oil from the oilpassages 3a and 3b and slide down at the heads along the slanted surfaceof the thrust bearing so as to generate a torque, thereby rotating thecylinder block 11 and motor shaft 5.

The thrust bearing 16 is supported by an annular support 35 in relationof being slanted at a predetermined angle, the annular support 35 beingfixedly sandwiched between the upper and lower half casings 1 and 2.

The motor shaft 5 is provided at one axial end journalled to the centersection 3 with a spherical bush 33 and at the other end with a sphericalbush 34, which are sandwiched between the upper and lower half casings Iand 2.

A gear 17 is mounted on the motor shaft 5 and engages with a gear 21 onthe counter shaft 24, the gears 17 and 21 constituting the firstdeceleration means or first reducing gear unit (FIGS. 3 and 11). Thecounter shaft 24 provides means for transmitting power from thehydraulic motor M. As best seen in FIG. 3, the longitudinal axes of themotor shaft and the counter shaft are parallel to the longitudinal axisof the axle.

A small diameter gear 22 on the counter shaft 24 engages with a ringgear 23 at a differential gear unit D, which gives differentialrotations to drive the axles 13.

The small diameter gear 22 and ring gear 23 constitute the seconddeceleration means or second reducing gear unit.

A brake drum 18 is fixed to the foremost end of the motor shaft 5 andbrake shoes are expanded radially outwardly by a brake lever 19 tocontact with the brake drum 18, thereby exerting the braking action.

In FIG. 6, part of motor mounting surface 3e, against which the cylinderblock 11 (see FIG. 2) for the hydraulic motor M abuts, is shown.

Referring to FIGS. 7, 8, 9 and 10, a modified embodiment of the axledriving apparatus of the invention will be described.

In the embodiment shown in FIGS. 2 and 3, the oil passages 3a and 3b andsupply oil passage 30 are provided at the same plane, but in this case,the motor mounting surface 3e must separate with respect to the pumpmounting surface 3d, whereby the center section 3 cannot be compact tothat extent and also the casing becomes larger.

Therefore, in the embodiment shown in FIGS. 7-10, in order to eliminatethe above defects, the supply oil passage 30 is disposed to overlap withthe oil passages 3a and 3b in a range of thickness of the lower portionof the center section 3 and below the oil passages 3a and 3b.

The supply oil passage 30 is bored to communicate at the upper halfthereof with the lower halves of the oil passages 3a and 3b in a mannerof overlapping therewith. Hence, the oil passage connecting both the oilpassages 30 and 3a, 3b is not required, thereby enabling the centersection 3 to be made as small as possible in thickness.

At the center of the supply oil passage 30 is open an operating oilsuction port 3c toward an oil filter 8 positioned below, and checkvalves 26 and 27 for opening or closing the communicating portionbetween the oil passages 3a and 3b are interposed in the supply oilpassage 30 in relation of putting the operating oil suction port 3cbetween the check valves 26 and 27. Supply oil from the operating oilsuction port 3c flows to the oil passages 3a and 3b though the portionat the supply oil passage 30 where the supply oil passes the checkvalves 26 and 27.

Thus, within the center section 3, the oil passages 3a and 3b, supplyoil passage 30 and oil filter 8 overlap with each other, whereby themotor mounting surface 3e can approach the pump mounting surface 3d soas to enable the center section 3 to be compact.

Next, explanation will be given on the embodiment in FIGS. 12 and 13.

In this embodiment, a center section 3 abuts from above against theinner surface of the bottom wall of the lower half casing 2 and is fixedthereto.

Bolts 39 for fixing the center section 3 also are inserted from aboveinto the bolt bores and screw with the lower half casing 2 respectively.

The center section 3 in this embodiment, as shown in the sectional frontview of FIG. 12, is about L-like shaped. The pump mounting surface 3d isformed on the longer part of the L-shape, while the motor mountingsurface 3e is formed on the shorter part of the L-shape, perpendicularto the pump mounting surface.

Other constructions of this embodiment are about the same as theaforesaid embodiment.

Next, explanation will be given on the embodiment in FIGS. 14, 15 and16.

In this embodiment, three bolt bores 3g for three bolts 39 for fixingthe center section 3 to the lower surface of the upper half casing 1 areprovided at the center section 3, the three bolts 39 fixing the centersection 3 at the casing mounting surface to the upper half casing 1.

The center section 3 and upper half casing 1 constitute material withaluminum die casting, the mounting surfaces of both the members beingnot applied with machining.

Rather than using four bolts 39 to fix the center section 3, in which anerror in material may distort the section and prevent a tight fit, inthe present invention three bolts 39 are inserted into three bolt bores3g to fix the center section 3, thereby keeping all the-bolts in-goodtight conditions.

In the embodiment in FIGS. 14, 15 and 16, the pump mounting surface 3dis not adjacent to the motor mounting surface 3e at the center section3, but rather is adjacent to the axle 13. Additionally, as can best beseen in FIG. 15, pump mounting surface 3d is disposed between thelongitudinal axis 13 x of the axle shafts 13 and the longitudinal axis5x of output shaft 5. Pump mounting surface 3d is offset from thelongitudinal axis 5x of output shaft 5 by the distance ΔH.

Oil passages 3a and 3b are bored from a pair of crescent-shaped oilpassages provided at the motor mounting surface 3e and extend inparallel to the axles 13, oil passages 3m and 3n being bored at a sideof center section 3 from a pair of crescent-shaped oil passages andextending perpendicularly to the axles 13, so that both oil passages 3mand 3a and 3n and 3b are communicating with each other in the centersection 3.

The open ends of oil passages 3m and 3n are plugged and the plugs arelocked by projections formed at the bottom of the lower half casing 2respectively.

Check valves 36 and 37 are provided at open ends of oil passages 3a and3b, valve levers 36b and 37b of which are connected to a leaf spring 38.

The valve levers 36b and 37b are open only in the direction of flowingoil from the operating oil suction ports 3p and 3q into the oil passages3a and 3b. The check valves 36 and 37 flow into the oil passages 3a and3b the supply operating oil after passing the plate-like oil filter 8,and discharge to the exterior the pressure oil in oil passages 3a and 3bby pushing the valve levers 36b and 37b through the leaf spring 38pushed by a control 7, thereby serving as the short circuit valves tocause the free condition of hydraulic motor M.

As seen from the above discussion, the center section 3 carrying thehydraulic pump P and its shaft 4 vertically and the hydraulic motor Mand its shaft 5 horizontally (whereby the longitudinal axis of the pumpinput shaft is perpendicular to the longitudinal axes of the motoroutput shaft and the axle) is provided, and contained within thetransmission casing while carrying both the pump P and motor M, wherebythe operating oil, even when leaked from the hydraulic pump P orhydraulic motor M, does not flow out to the exterior. Also, since theoil passages are formed at the center section 3, no piping is requiredin or out of the transmission casing.

The center section 3 is fixed to the upper half casing 1 or the lowerhalf casing 2, thereby being simple to support. Also, the pump shaft 4and motor shaft 5 are simple to support.

The pump mounting surface 3d and motor mounting surface 3e are disposedin an L-like shape and the center suction 3 is about L-like shaped whenviewed in section, so that the pump shaft 4 or input means is verticaland the motor shaft 5 or output means is horizontal, thereby making theaxle driving apparatus compact without interposing the bevel gears, andthe power transmitting direction can be changed at an angle of 90°,thereby having advantages for the tractor loading a vertical outputshaft-type engine.

The center section 3 is fixed to the lower side of the butt jointsurface of the upper half casing 1 so that the pump mounting surface 3dis level with the mounting surface of the center section 3 to the upperhalf casing, whereby the surfaces of the upper half casing 1, lower halfcasing 2 and center section 3 can be restricted to a minimum.

Three bores 3g for the three fixing bolts 39 through which the centersection 3 is fixed to the lower surface of the upper half casing 1 areformed, so that when the mounting surfaces of center section 3 and ofupper half casing 1 are fixed as they are not flattened but cast, thereis no fear that a poor tightening condition is created on the centersection 3.

The spherical bushing 32 at the pump shaft 4 and spherical bushing atthe bearing for the motor shaft 5 are used, so that even when the centersection 3 is mounted slantwise due to an assembly error or a machiningerror, variations in orientation of the pump shaft 4 or the motor shaft5 is absorbable.

Also, the spherical bushings are smaller in the size than the usualbearing, whereby the bearing is disposable without interfering with theoil passages bored at the center section.

Although several embodiments have been described, they are merelyexemplary of the invention and not to be construed as limiting, theinvention being defined solely by the appended claims.

What is claimed is:
 1. A hydraulic transaxle, comprising:a casing formedof a first casing section and a second casing section joined along ajunction surface, said junction surface defining a plane; a pair of axleshafts having a longitudinal axis rotatably supported by said casing,wherein each of said pair of axle shafts extends in a direction oppositeto the other of said pair; a hydrostatic transmission for driving saidpair of axle shafts including a hydraulic pump and a hydraulic motor,said hydraulic motor including output means having a longitudinal axis;a brake coupled to said output means; transmitting means having alongitudinal axis disposed within said casing for transmitting powerfrom said hydraulic motor; a differential gear unit disposed within saidcasing and connecting said transmitting means and said pair of axleshafts, said differential gear unit driving said pair of axle shafts;and input means for transmitting power to said hydraulic pump.
 2. Ahydraulic transaxle according to claim 1, wherein said hydraulic pump isdisposed between the longitudinal axis of said pair of axle shafts andthe longitudinal axis of said output means.
 3. A hydraulic transaxleaccording to claim 1, wherein said output means comprises an outputshaft.
 4. A hydraulic transaxle, comprising:a casing formed of a firstcasing section and a second casing section joined along a junctionsurface, said junction surface defining a plane; a pair of axle shaftshaving a longitudinal axis rotatably supported by said casing, whereineach of said pair of axle shafts extends in a direction opposite to theother of said pair; a hydrostatic transmission for driving said pair ofaxle shafts including a hydraulic pump and a hydraulic motor, saidhydraulic motor including output means having a longitudinal axis,wherein the longitudinal axis of said output means is disposed in saidplane; transmitting means having a longitudinal axis disposed withinsaid casing for transmitting power from said hydraulic motor; adifferential gear unit disposed within said casing and connecting saidtransmitting means and said pair of axle shafts, said differential gearunit driving said pair of axle shafts; and input means for transmittingpower to said hydraulic pump.
 5. A hydraulic transaxle according toclaim 4, wherein said hydraulic pump is disposed between thelongitudinal axis of said pair of axle shafts and the longitudinal axisof said output means.
 6. A hydraulic transaxle according to claim 4,wherein said output means comprises an output shaft.
 7. A hydraulictransaxle according to claim 4, further comprising a brake coupled tosaid output means.
 8. A hydraulic transaxle, comprising:a casing formedof a first casing section and a second casing section joined along ajunction surface, said junction surface defining a plane; a pair of axleshafts having a longitudinal axis rotatably supported by said casing,wherein each one of said pair of axle shafts extends in a directionopposite to the other of said pair; a hydrostatic transmission fordriving said pair of axle shafts including a hydraulic pump and ahydraulic motor, said hydraulic motor including an output meanscomprising an output shaft having a longitudinal axis parallel to saidlongitudinal axis of said pair of axle shafts; a brake coupled to saidoutput means; a transmitting means having a longitudinal axis parallelto said longitudinal axis of said pair of axle shafts and said outputshaft disposed within said casing for transmitting power from saidhydraulic motor; a differential gear unit disposed within said casingand connecting said transmitting means and said pair of axle shafts,said differential gear unit driving said pair of axle shafts; adeceleration means for operably connecting said hydrostatic transmissionand said differential gear unit, wherein said differential gear unit andsaid deceleration means are disposed within said casing; and an inputmeans for transmitting power to said hydraulic pump.
 9. A hydraulictransaxle according to claim 8, wherein said deceleration means includesa first deceleration means and a second deceleration means.
 10. Ahydraulic transaxle according to claim 9, wherein said transmittingmeans comprises a counter shaft, and said first deceleration meanscomprises a gear on said output shaft and a gear on said counter shaft.11. A hydraulic transaxle according to claim 10, wherein said seconddeceleration means comprises a gear on said counter shaft and a gear ofsaid differential gear unit.
 12. A hydraulic transaxle according toclaim 8, wherein said brake is fixed to said output shaft.
 13. Ahydraulic transaxle according to claim 8, wherein said longitudinal axisof said pair of axle shafts lies in said plane of said junction surface.14. A hydraulic transaxle according to claim 13, wherein saidlongitudinal axis of said output shaft lies in said plane of saidjunction surface.
 15. A hydraulic transaxle, comprising:a casing formedof a first casing section and a second casing section joined along ajunction surface, said junction surface defining a plane; a pair of axleshafts having a longitudinal axis rotatably supported by said casing,wherein each one of said pair of axle shafts extends in a directionopposite to the other of said pair; a hydrostatic transmission fordriving said pair of axle shafts including a hydraulic pump and ahydraulic motor, said hydraulic motor including an output means having arotational axis which is disposed in said plane of said junctionsurface; a transmitting means having a longitudinal axis disposed withinsaid casing for transmitting power from said hydraulic motor; adifferential gear unit disposed within said casing and connecting saidtransmitting means and said pair of axle shafts, said differential gearunit driving said pair of axle shafts; and an input means fortransmitting power to said hydraulic pump having a rotational axis;wherein said rotational axis of said input means is substantiallyperpendicular to said rotational axis said output means.
 16. A hydraulictransaxle according to claim 15, wherein said output means is a motorshaft.
 17. A hydraulic transaxle according to claim 15, furthercomprising a brake coupled to said output means.
 18. A hydraulictransaxle according to claim 17, wherein said output means is a motorshaft.
 19. A hydraulic transaxle according to claim 18, wherein saidbrake is fixed to said motor shaft.
 20. A hydraulic transaxle accordingto claim 15, wherein said longitudinal axis of said pair of axle shaftslies in said plane of said junction surface.
 21. A hydraulic transaxleaccording to claim 15, wherein said rotational axis of said output meanslies in said plane of said junction surface.